In the prior art, for example Shockey et al. U.S. Pat. No. 4,994,033 and the C. R. Bard, Inc. European patent application no. 383,429 A2, published Aug. 22, 1990, a catheter is taught for the application of medication to a blood vessel wall, for example to a stenosis. The medication is administered through a balloon in the catheter which carries an array of minute holes or micropores, so that the medication may flow into the balloon through a lumen in the catheter, and then by the action of pressurization in the balloon it is forced out of the holes or micropores.
It has been found that at pressures of about two atmospheres and above, the velocity of fluid that passes out of the holes of such a balloon often can create a forceful stream which directly impinges the arterial wall. This, in turn, can actually cause tissue damage, even to the extent of extending and increasing the dissection within the arterial wall which is caused by an angioplasty procedure such as PTCA.
Thus, there is a need for a therapeutic balloon catheter for administering medication to the artery wall in which the medication can be administered under a reasonable pressure for rapid flow of medication out of a perforated balloon, but the forceful stream is avoided, so that the fluid does not forcefully impinge the arterial wall, but rather "weeps" out of the perforations in a substantial but non-damaging manner.